1. Field of the Invention
The invention relates to a thin film recording head for use with a magnetic recording device such as a magnetic disk, and also to a method for manufacturing, such a thin film.
2. Description of the Related Art
FIG. 1 is a cross-sectional view illustrating a prior thin film head. The prior thin film is manufactured generally as follows. First, on an Al.sub.2 O.sub.3 -TiC substrate 1 is formed an insulative layer 2 composed of alumina by means of sputtering. Then, on the insulative layer 2 is formed a lower magnetic layer 3 by sputtering or plating soft magnetic substance such as a permalloy. On the lower pole layer 3 is then formed an insulative gap layer 4 composed of alumina and having a predetermined thickness. Then, an unnecessary rear portion of the insulative gap layer 4 is removed by etching. Then, photoresist is applied on the insulative gap layer 4 by the spin-coating process in order to eliminate an irregularity due to the lower magnetic layer 3. Then, a resulting structure subjected is to heat treatment at approximately 250 degrees centigrade to form a hard-cured photoresist layer 5a.
Then, on the hard-cured photoresist layer 5a is formed a first layer which is to act as a layer for preventing the photoresist layer 5a from peeling off, and on the first layer is formed a second layer which is to act as a underlying layer for plating. The first and second layers are formed by means of sputtering. Then, a coil layer is patterned on the second layer with photoresist, and then coils 6 are formed by means of plating. Then, the photoresist having been used for coil patterning is removed, and further unnecessary portions of the first and second layers are removed by ion-milling in order to smooth irregularities formed by the coils 6, photoresist is applied over the coils 6, and then subject to a heat treatment at 250 degrees centigrade. Thus, there is formed a hard-cured photoresist layer 5b. Then, on the insulative hard-cured photoresist layer 5b is formed an upper magnetic layer 7 in a similar way as that of the lower magnetic layer 3. Thus, a transducer portion of a thin film recording head is completed. The hard-cured photoresist layer 5b provides many advantages. For instance, the hard-cured photoresist layer 5b eliminates irregularities formed by the coils 6, enhances electrical insulation, and smoothes a shoulder portion indicated with C and C'.
Recently, with down-sizing of a device and high densification of magnetic recording, a space between a head and a medium has been much reduced. As a result, it is required to apply a certain plus voltage (for instance, +6 V) to a coil for operating a transistor-driver circuit. However, it has been found that if a prior thin film head would be used for applying a certain voltage to a coil, there occurs dielectric breakdown of a head and an output voltage of a head is decreased to thereby produce a larger noise.